Fiber optic manufacturing in space

ABSTRACT

Aspects of the embodiments are directed to systems and methods for forming an optical fiber in a low gravity environment, and an optical fiber formed in a low gravity environment. The system can include a preform holder configured to secure a preform; a heating element secured to a heating element stage and residing adjacent the preform holder; a heating element stage motor configured to move the heating element stage; a tension sensor; a spool; a spool tension motor coupled to the spool and configured to rotate the spool; and a control system communicably coupled to the heating element stage motor and the spool tension motor and configured to control the movement of the heating element stage based on a rotational speed of the spool. The optical fiber can include a fluoride composition, such ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN), and can be characterized by an insertion loss in a range from 13 dB/1000 km to 120 dB/1000 km.

CROSS REFERENCE TO RELATED APPLICATION

This patent application claims the benefit, pursuant to 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 62/295,478,titled, “Fiber Optic Manufacturing in Space,” filed on Feb. 15, 2016,the entire contents of which are incorporated by reference herein.

TECHNICAL FIELD

This disclosure pertains to fiber optic manufacturing in space, andapparatuses and methods for achieving the same.

BACKGROUND

An optical fiber (or fibre) is a flexible, transparent fiber, often madeof glass (silica) or plastic. Optical fibers are used to transmit lightbetween the two ends of the fiber, and have practical applications inthe fields of fiber-optic communications, where they permit transmissionover longer distances and at higher bandwidths (data rates) than wirecables. Optical fibers exhibit low attenuation characteristics and lowelectromagnetic interference, as compared to metal wires. Thereforeoptical fibers can accommodate higher bandwidth, as mentioned, and/orlonger transmission distances. Optical fiber has other uses, such as inlaser applications, imaging applications, and lighting applications.

SUMMARY

Aspects of the embodiments are directed to a system for forming anoptical fiber in a low gravity environment. The system can include apreform holder configured to secure a preform; a heating element securedto a heating element stage and residing adjacent the preform holder; aheating element stage motor configured to move the heating elementstage; a tension sensor; a spool; a spool tension motor coupled to thespool and configured to rotate the spool; and a control systemcommunicably coupled to the heating element stage motor and the spooltension motor and configured to control the movement of the heatingelement stage based on a rotational speed of the spool.

Aspects of the embodiments are directed to a method for forming anoptical fiber in a low gravity environment. The method can includeproviding a preform in a preform drawing apparatus in the low gravityenvironment; engaging the preform with a spool under an initialtemperature; turning the spool until a desired tension on the preformhas been reached; increasing the temperature of the preform until adesired spool speed is reached; and locking the temperature of thepreform.

Aspects of the embodiments are directed to an optical fiber drawn in alow gravity environment. In some embodiments, the optical fibercomprises fluoride, such as ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN). In someembodiments, the optical fiber comprises an insertion loss in a rangefrom 13 dB per 1000 km to 120 dB per 1000 km.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example apparatus for materialprocessing in low in accordance with embodiments of the presentdisclosure.

FIG. 2 is a schematic diagram of another example apparatus for materialprocessing in low in accordance with embodiments of the presentdisclosure.

FIG. 3 is a schematic diagram of a controller for fabrication of theoptical fiber in low gravity environment in accordance with embodimentsof the present disclosure.

FIG. 4 is a schematic diagram of a logical diagram for an optical fiberdrawing apparatus in accordance with embodiments of the presentdisclosure.

FIG. 5 is a process flow diagram for drawing an optical fiber in lowgravity environments in accordance with embodiments of the presentdisclosure.

FIG. 6 is a schematic diagram of a data transmitter using an opticalfiber in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

This disclosure describes an optical fiber that is formed in low gravityenvironments, such as aboard space-borne vehicles or platforms, andmethods and devices for making optical fibers in low gravityenvironments. In this disclosure, the term “low gravity” can includesgravitational forces wherein g≤10⁻² G for two or more minutes. Anexample space-borne vehicle/platform can include the International SpaceStation (ISS), other orbital platforms, or orbital vehicles.

Optical fibers made from glasses with low insertion loss in infraredspectral range, such as fluoride-based optical fibers, including ZBLAN(ZrF4-BaF2-LaF3-AlF3-NaF), have the potential to enhance opticalcommunications beyond that of conventional fused silica based opticalfibers. For example, non-fluoride-based optical fibers made from fusedsilica are currently approaching the theoretical limit of insertion lossof 0.14 dB/km or 140 dB per 1000 km, with actual insertion loss under200 dB per 1000 km. ZBLAN optical fibers have been characterized ashaving a theoretical minimum insertion loss of 13-22 dB per 1000 km.ZBLAN optical fibers, however, can undergo errant crystallization anddetrimental phase separation during fabrication, and these factors ofcrystallization and phase separation can inhibit reaching thetheoretically low loss. These crystallization and phase separationphenomena are suppressed in low gravity environments. This disclosuredescribes systems and methods for manufacturing optical fibers that canachieve the insertion loss in the infrared spectrum of less than 0.12dB/km in its undoped form.

The low insertion loss of ZBLAN optical fiber in combination with aunique transparency window from UV down to mid-IR wavelengths makes thisfluoride-based optical fiber a strong candidate for broadband spectralsignature recording, environmental monitoring, mid-IR fiber lasers formedical and military needs with a potential of reducing the transmissionloss by an order of magnitude compared to the best existingtelecommunication fibers that would revolutionize opticalcommunications.

Due to its high value-to-mass ratio and unique enhancements in zerogravity the optical fiber production shows promise for a commerciallyattractive process for the orbital platform. This disclosure describesforming ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) optical fibers (and/or opticalfibers having similar properties as ZBLAN optical fiber) in low gravity.

Material Processing Apparatus for Low Gravity Environment

The low gravity environment, such as the microgravity environment oforbital space flight, can change a number of chemical, physical,biological and other processes that are widely used in various processesin normal gravity environment on Earth. A good illustration of adifference in processing that occurs between low gravity and normalgravity is a process of burning. A round shape and uniform glow formwhen burning in low gravity due to lack of convection process (i.e.,when hot air moves up and shapes up the flame). One of the implicationsof such a difference is the possibility to use the low gravity orbitalenvironment for manufacturing processes that are not possible on Earth.Additionally, low gravity environments can foster the elimination ofbouncy differences in multicomponent material systems, such asmulticomponent glasses or crystals with defects, resulting in bettermaterial uniformity during the processing and allowing to obtain uniquematerial properties that may not be available on Earth. Examples of themanufacturing processes are the glass fiber drawing and crystalprocessing including defect elimination and crystal growth. The presentdisclosure describes the apparatus and the process details that allowthe optimal utilization of the microgravity environment.

FIG. 1 is an apparatus 100 for material processing in low in accordancewith embodiments of the present disclosure. The apparatus 100 is mountedon a support 105 that provides structural integrity of the apparatus100. The support has a mount 107 for attaching the apparatus duringlaunch of the rocket to the space platform during operation in space. Anoptimal platform for volume low gravity processing is an orbital stationsuch as International Space Station. The design of the mount 107establishes reliable mechanical connection and can be also used toreduce (damp) the vibration transfer from the mounting location. Theapparatus has a shield 110 that provides isolation of the apparatus fromthe space environment during operation and rocket environment during thepreparation for launch and during trip on a rocket to space. Theshielding 110 allows the establishment of a processing-specificenvironment for the apparatus. An example of such an environment is lowpressure environment. Another example of such environment is gas fillsuch as formic gas with hydrogen content and without oxygen thatprevents oxidation or chlorine gas that suppresses water relatedreactions. Another example is the dry air environment with reduced watervapor content.

A material sample 115 is placed inside the apparatus for processing inlow gravity. The example of such material is a multicomponent glass suchas fluoride glass composition, for example ZBLAN glass with acomposition ZrF4-BaF2-LaF3-AlF3-NaF. This material sample 115 (alsoreferred to as a preform) can be coated with protective material such asfluoride polymer, such as Teflon. Preferably the softening temperatureof the coating material such as polymer is lower than the processingtemperature of the glass preform. Another example of such materialsample 115 is a crystal, for example gallium nitride or silicon carbidecrystals that can be in a form of a wafer and may have defects. Thesection (zone) of the material sample 120 represents the portion of thesample that undergoes transformation. The transformation example is thedraw of the optical fiber from the fiber preform under applied heat thatsoftens the preform. Another example of the transformation is crystalproperties change and the transition zone 120 is the section of thesample where for example crystallization or re-crystallization occurs.In another configuration the section 120 is the section of the crystalwhere the defects of the crystalline structure are removed during theprocessing in low gravity. In another configuration for zone meltingthis section is molten material zone that drives the impurities from thesample. The transformed material 122 is the continuation of the materialsample past the transformation portion. In the case of fiber draw thetransformed material results in optical fiber. In case of crystalgrowth, the transformed material is crystal. In case of crystal withdefects processing the transformed material is the crystal with lowamount of defects. In case of zone melting this is processed materialwith low amount of impurities. The material sample 115 is mounted with apreform holder 125. The mount could be a sample holder with alignmentelements that provide the orientation adjustment and positioning of thematerial sample 115 for optimal processing. The preform holder 125 mayhave a locking mechanism for protection of the material sample 115during the delivery of apparatus 100 to the low gravity environment. Thepreform holder 125 is attached to the support 105 with the interface130. This interface 130 can have a tension load cell that facilitatesmonitoring of the material transformation.

A transformation actuator 135 facilitates the transition of material 115to the resulting material 122. Most common example of the actuator is aheating oven. Alternatively the actuator could be a laser. An additionalalignment element that can align the position of the fiber preform 115relative to the actuator 135 could be mounted on the actuator 135. Thisalignment element can be a centering fixture to keep the preform 115 inthe center portion of the oven without touching the oven walls. Thetransformation actuator 135 is mounted on support 150. The support 150can include a mechanism to adjust transformation actuator 135. Forexample, the support can adjust the position of the heating oven overthe transition zone 120 for optimal transformation. The sensor element155 is mounted on the support 150 with attachment element 160 that mayalso have adjustment capability. The sensor element 155 is used tomonitor the transition zone 120. This monitoring can be done within thetransformation actuator 135 to control the transition process throughadjustment of transformation actuator 135 performance. Thetransformation actuator 135 could be a temperature measurement device,for example a thermal camera or a remote thermometer with a laserpointer. The mounting interface 145 is used to attach the support 150 tothe support 105. The mounting interface 145 can contain the translationstage for moving the transformation actuator 135 along the length ofmaterial 115 to facilitate the transformation along the element 115.

The spool 165 serves as collecting element for collecting thetransformed material 122. This spool 165 can be a fiber spool in case ofa fiber draw. In one embodiment this fiber spool 165 can prevent thecollected fiber 122 from de-spooling in case of breaking of the fiber122. The spool 165 is a crystal holding container in case of the crystalgrowth. The spool 165 is attached to the mounting interface 175 with theholding element 170. The holding element 170 could be a spoolingmechanism that rotates the spool 165 for winding the resulting fiber122. The mounting interface 170 could be a translation stage thatprovides uniform winding of the fiber across the spool.

The apparatus 100 as a whole could be made in a form of a processingcontainer. Alternatively the set of elements of apparatus 100 could bemade in a form of a container similar to a cassette for travelling up tolow gravity environment and back while the remaining set of parts ofapparatus 100 are staying stationary in low gravity environmentsimilarly to cassette deck that accepts the cassette (or multiplecassettes), plays the cassette for material transformation. After theprocessing the cassette portion of the apparatus 100 is returned back toEarth for orbital material use.

FIG. 2 is a schematic diagram of another example fiber draw apparatus200 for low gravity environment in accordance with embodiments of thepresent disclosure. Apparatus 200 is similar to apparatus 100. Apparatus200 includes a preform container 202. Preform container 202 includes apreform holder 206 that holds a preform 204. Preform 204 can be afluoride-based material for forming fluoride-based optical fiber 216. Inone example, the preform 204 can be a ZBLAN preform.

The preform container 202 can include an oven stage 208. The oven stage208 can be coupled to an oven stage motor 214. Oven stage motor 214 canbe controlled to move the oven stage 208 along the length of the preform204 as the preform 204 shortens due to being drawn into fiber 216. Theoven stage motor 214 can be driven by a controller (shown in more detailin FIG. 3) that uses certain inputs to control the speed of the ovenstage 208 translation. The controller can also control the temperatureof the oven. The oven stage motor 214 can also be controlled based oninformation from a profile sensor 210 and/or an oven camera 212. Theoven camera 212 records the tip of the preform condition in thetransformation zone. The preform 204 can be further illuminated from theback side with the light source such as light emitting diode (LED) orthe laser. The image of the preform tip inside the oven 209 is used todetect crystallization and the defects of non-uniformity that producelight scattering. The fabrication process parameters are optimized forhaving minimal amount of defects using the oven camera image. The ovenstage motor 214 can also control the spooling of the fiber 216, asdescribed further below.

The apparatus 200 also includes a tension sensor 218 that monitors thetension of the fiber 216 prior to spooling. The tension sensor 218 canprovide an input to the controller to control one or more parameters,such as the oven stage motor control. In apparatus 200, a tension sensor218 is shown between the preform 204 and the spool 220. A tension sensor207 can also (or in the alternative) reside on the preform holder 206 tocontact the preform 204.

In embodiments, the oven temperature can be fixed. The measured tensionof the draw is used to control the oven stage motor 214. Therefore, thespeed of the spool 220 controls the speed of the oven stage 208. Byallowing the spool 220 to control the speed of the oven stage 208, thediameter of the fiber 216 is controlled by the ratio of the speed of thespooling relative to the movement of the oven stage 208. At the outset,the spool 220 can be engaged to provide an initial tension on theexposed preform 204. A controller (of FIG. 3) can control a spooltension motor 222 to create a draw tension. The controller can stop thespool tension motor 222 from rotating the spool after a target drawtension is reached, as indicated by tension sensor 207, whilemaintaining the draw tension on the fiber 216. When the target tensionis reached, the oven 209 can be activated to heat the preform 204. Theoven temperature can be gradually increased until a desired spool speedis reached. The fiber 216 will begin to draw when the preform 204reaches a minimum draw temperature. This temperature is defined by theminimum temperature needed to soften the preform 204 such that the fiber216 can be drawn from the preform 204 at the target tension. Since thespool 220 is under a torque load by the spool tension motor 222, thespool 220 will rotate to draw the fiber 216.

In embodiments, the draw tension and the draw temperature can beindependently optimized. For example, a high temperature and low drawtension can increase optical fiber purity and decrease the likelihood ofadditional strain placed on the fiber during drawing. Additionally, thediameter of the optical fiber 216 can also be independently controlledby optimizing the ratio of the spool speed to the oven stage movementspeed. One advantage of drawing the optical fiber in a low gravityenvironment is that the change in the weight of the preform 204 does notneed to be monitored.

The spool tension motor 222 includes a safety limiter that limits thetorque that the motor can apply on the spool 220. The safety limiter canprevent the spool tension motor 222 from over-driving the spool 220 andbreaking the fiber 216.

In embodiments, the coating material can be on the preform 204 prior toheating. In embodiments, the oven stage 208 can include a coatingmaterial holder 210 that can hold coating materials, such as Teflon. Thecoating materials can be heated in oven 208 during the fiber draw. Thecoating material holder 210 can be coupled to the oven stage 208 to movewith the oven stage 208 by oven stage motor 214. Adding the coating,such as Teflon, to the fiber during formation can be performed in amanner similar to that described in U.S. patent application Ser. No.10/131,970, titled, “Method for forming a protective coating on anoptical fiber,” filed on Apr. 24, 2002, the entire contents of which areincorporated by reference.

The apparatus 200 also includes a spool linear stage 224 and a spoolstage motor 226. The spool linear stage 224 can be moved by the spoolstage motor 226 to allow the spool 220 to wind the drawn fiber 216around the spool 220.

FIG. 3 is a schematic of a control system 300 for fabrication of theoptical fiber in low gravity environment in accordance with embodimentsof the present disclosure. The control system can include amicrocontroller 302. Microcontroller 302 can be a microprocessor orother computing element that is able to control various motors of theapparatus 100 or 200 based on certain inputs. For example, themicrocontroller 302 can receive as an input oven temperature 304 from anoven thermometer, fiber tension 306 from a tension sensor, and a spoolspeed 308 from a spool tension motor, and an oven stage speed 310 fromthe oven stage motor.

FIG. 4 is a schematic diagram of a logical diagram 400 for an opticalfiber drawing apparatus in accordance with embodiments of the presentdisclosure. The logical diagram 400 illustrates example logicalcommunication paths between various aspects of a low gravity opticalfiber drawing apparatus (such as apparatus 100 or apparatus 200). Thecontrol system 300 can be communicably coupled to a tension sensor (suchas tension sensor 207), an oven 209 (or, more specifically, an oventhermometer to control oven temperature), a spool tension motor 222 (tocontrol the tension of the fiber), an oven stage motor 208 (to controlthe movement of the oven 209 relative to the preform 202), and a spoolstage motor 226 (to control translation of a spool stage to accommodatewinding of the optical fiber across the spool).

FIG. 5 is a process flow diagram 500 for drawing an optical fiber in alow gravity environment in accordance with embodiments of the presentdisclosure. At the outset, the preform can be provided in a low gravityenvironment, such as an orbital platform or orbital vehicle (502).During transport to the orbital platform or vehicle, the preform (in apreform holder) and the spool are locked in place. When ready foroperation, the interlocks can be disengaged. The preform can be heatedto a predetermined initial temperature to soften the preform forengagement to a spool (504). A coating material can also be heated(506), and the coating covers the drawn fiber. The preform can then beengaged with the spool for drawing (508). A torque can be applied to thespool to pull the fiber and apply an initial tension on the preform(510). While the torque is applied, the spool will turn until a desiredtension is met (512). The spool will stop turning at when the desiredtension is met. The controller can then gradually apply heat to thepreform (e.g., by the oven) to further soften the preform and cause thespool to turn as the preform softens (514). The spool speed is monitoredunder a constant tension and increasing heat until a desired spool speedis reached (516). Once the desired spool speed is reached, the heat islocked (518). The spool speed can be used to control the oven stagemotor to move the oven stage as the preform/fiber interface changes(520). For example, for a desired fiber diameter, a ratio of spool speedto oven stage movement speed can be determined. The process can continueuntil the preform has been exhausted. In embodiments, the tension, oventemperature, spool speed, and oven stage speed can be changed for asingle preform to obtain optical fibers with different characteristics.

In a first example, embodiments of the present disclosure can include anapparatus that includes a preform material held in place by a preformholder. The preform can include a glass or crystal material and can becovered by a coating. The apparatus also includes a transform apparatus(e.g., an oven) residing adjacent to the preform holder, wherein thepreform can reside at least partially in the oven. The transformapparatus can be on a moveable stage (moveable relative to the preformholder). The transform apparatus is configured to heat the preform to alevel to facilitate transformation of the preform into a fiber materialhaving a different material composition than the starting preform. Theapparatus also includes a shield or cover that can create an air-tightchamber that houses the preform holder, the transform apparatus, andother components.

In some embodiments, the apparatus includes a spool to wind the fibermaterial.

In some embodiments, the apparatus includes a load cell coupled to thepreform holder to measure the tension placed on the preform and thefiber as it spools.

In some embodiments, the apparatus can be housed in a cassette formfactor housing.

In some embodiments, the apparatus includes a thermal camera to monitorthe preform cone temperature.

In some embodiments, the apparatus includes a surfacing coatingimplementing device that allows for the fiber to be drawn with acoating, such as a high fluorine material, such as a Teflon coating.

Optical fiber fabrication in space can be a costly process that includesthe delivery of the preform mass to the space platform and subsequentrecovery of the resulting optical fiber on the ground. The environmentalsensitivity of the low loss infrared materials, such as fluorideglasses, requires the protection of the preforms and the resultingoptical fibers. In conventional optical fibers for telecommunications,the weight of the polymer coating is roughly the same as the weight ofthe fiber itself. For space manufacturing, the processing of the fiberin space that includes a primary coating. The primary coating representsa fraction of the infrared glass material weight, for example less thanhalf of the infrared glass preform weight. The optical fiber that isfabricated in space can then be coated with a secondary coating upon thereturn to Earth. This secondary coating could be applied over theprimary coating.

In some embodiments, the primary coating can be removed before thesecondary coating application. The protection of the fiber can beachieved through the coating of the preform with the polymer materialthat is similar in softening temperature to the fiber preform. Suchmaterial could be Teflon polymer coating. The fiber draw happenstogether with the coating draw in space, resulting in Teflon coatedoptical fiber. Preferably the softening temperature of the coatingshould be less than the softening temperature of the glass.Alternatively, the low loss infrared material preform could be coatedwith the glass material with similar softening temperature. Theadvantage of using the glass layer protection is that the glass layerprovides better environmental protection compared to the polymercoating.

Example Implementations

Remote Energy Delivery System

An optical fiber can be used as a medium for delivery of high laserenergy over great distances. With the dropping costs of the fiber-basedlasers, the use of the fiber energy delivery becomes an attractivesolution for a number of applications from powering the remoteinstallations to remote material processing including rock drilling andpipe perforation for energy industry.

The challenges of the existing fiber materials based on fused silicainclude the limited operating wavelength of approximately 1.6 micronsand fiber reach of approximately 5 km. The nonlinear effects and theinsertion loss in the fiber can limit the effective length and themaximum power of such systems.

Optical fiber energy delivery is also used for remote optical sensingand provides the benefit of the remote monitoring of structures over thegreat distances:

There is a promising solution for energy delivery through the fiberswith voids such as high-power infrared light delivery through a hollowcore photonic band gap fibers. The presence of the interfaces of fiberglass and the void in the optical path of such fibers however is aserious problem for high power delivery. The material defects of theinterface can degrade and create additional loss that will result infailed transmission.

The optical fiber described herein describes optical fiber materials andmanufacturing techniques for energy delivery. The fibers containinghalogen elements have the promise of insertion loss as low as 1 dB per1000 km.

Such fibers based for example on fluoride glasses provide the longeroperating length for the energy delivery system. The operatingwavelength of the new fibers is longer than 1.7 microns and preferablyis in the range of 2.0 to 6.5 microns. The reduced nonlinear effects andthe promise of lower insertion loss represent a unique opportunity toextend the length of the energy delivery and increase the deliveredoptical power. Suppression of loss-creating effects in the low gravityenvironment represents a unique opportunity to address the need with lowloss optical fibers made in a low obit platform.

The typical insertion loss for silica based optical fiber for powerdelivery is 0.2 dB per km. With acceptable power loss of 1 dB (˜20%) thedelivery range for such optical fibers is 5 km at the operatingwavelength around 1.5 microns.

The lower loss fibers described herein, such as fluoride based fibers,have can demonstrate insertion loss reduction down to the level of 0.02dB per km or less at the operating wavelengths longer than 1.7 microns.The resulting operating distance for such low loss fiber system with 1dB acceptable loss is increased beyond 10 km. The delivery of the lightwith longer wavelength provides additional benefits in the energyutilization due to higher absorption of the materials in the wavelengthrange from 1.7 microns to 6.5 microns. An example of such enhancedabsorption is the absorption of water that is widely presented in arange of materials and rocks at the wavelength range around 3 microns.

Optical Communication System with Longer Operating Wavelength andWavelength Conversion

FIG. 6 is a schematic diagram of a data transmission system 600 using anoptical fiber in accordance with embodiments of the present disclosure.The data transmission system 600 includes an optical fiber 602, whichcan be a fluoride or halogen based optical fiber manufactured in alow-gravity environment, as disclosed here. The data transmission system600 can also include wavelength conversion units 604 a and 604 b. Thewavelength conversion could be non-linear optical conversion. There is adramatic growth in the demand for fiber optic bandwidth that is drivenby the growth of data transmission. The upcoming challenge in addressingthe capacity scaling for the data transmission is facing the fundamentallimitations of existing fibers such as non-linear Shannon limit. Furtherincreases in the data transmission rates require the longer operatingwavelength and the lower loss optical fibers.

The fibers produced in a low gravity environment with the promise ofinsertion loss by more than an order of magnitude over existing opticalfibers offer both the reduced insertion loss and the longer operatingwavelength with reduced nonlinear effects for the data transmission.

The new low loss fibers represent the opportunity for new opticalcommunication system with wavelength conversion. This system operates atthe wavelength range that is longer than the typical wavelength ofexisting optical communications. The state of the art opticalcommunication systems operate at wavelength range at around 1.5 micronswith the typical fiber insertion loss in the range of 0.15 to 0.25 dBper km. The system of the present invention uses wavelength convertersto interface the low loss optical fibers with the data transmissions atshorter wavelength. The shorter wavelengths benefit from lower noise andlower cost optical detection and readily available high speed opticaltransmitters.

All-optical wavelength conversion in optical fibers has the followingpotential advantages: 1) it eliminates optical—electrical—opticalconversion and, thus, enables transparent all-optical networks; 2) it isultrafast and transparent to both modulation format and bit rate; 3) itinduces negligible signal degradation since there is little chirp oradded noise; and 4) the optical fiber itself is low cost, low loss, andseamlessly compatible with the transmission fiber.

The operating wavelength for the new low loss fiber is fromapproximately 1.7 microns to 6.5 microns. The wavelength of the opticalsignals after the wavelength converters is preferably in the range of0.7 microns to 1.5 microns to match the existing optical communicationsystems and low noise receivers.

What is claimed is:
 1. A system for forming an optical fiber in a lowgravity environment, the system comprising: a preform holder configuredto secure a preform; a heating element secured to a heating elementstage and residing adjacent the preform holder; a heating element stagemotor configured to move the heating element stage; a tension sensor; aspool; a spool tension motor coupled to the spool and configured torotate the spool; and a control system communicably coupled to theheating element stage motor and the spool tension motor and configuredto control the movement of the heating element stage based on arotational speed of the spool.
 2. The system of claim 1, furthercomprising a preform secured in the preform holder, wherein the tensionsensor is coupled to the preform holder and configured to monitor atension on the preform.
 3. The system of claim 2, wherein the heatingelement surrounds the preform.
 4. The system of claim 1, furthercomprising a spool translation motor configured to translate the spoolalong a long axis of the spool.
 5. The system of claim 1, wherein thecontrol system is configured to control a temperature of the heatingelement.
 6. The system of claim 1, wherein the control system isconfigured to control the spool tension motor to control a tensionapplied to a preform.
 7. The system of claim 1, wherein the tensionsensor comprises a load cell.
 8. The system of claim 1, furthercomprising a surface coating retention element surrounded by the heatingelement, the surface coating retention element configured to apply acoating onto a fiber.
 9. A method for forming an optical fiber in a lowgravity environment, the method comprising: providing a preform in apreform drawing apparatus in the low gravity environment; engaging thepreform with a spool under an initial temperature; turning the spooluntil a desired tension on the preform has been reached; increasing thetemperature of the preform until a desired spool speed is reached; andlocking the temperature of the preform.
 10. The method of claim 9,further comprising: heating a coating material with the preform; andcoating the optical fiber with the coating material during formation ofthe optical fiber.
 11. The method of claim 9, wherein increasing thetemperature of the preform comprises heating the preform in an oven thatsurrounds the preform.
 12. The method of claim 11, further comprisingadjusting a position of the oven as the preform changes, whereinadjusting the position of the oven is based, at least in part, on thespool speed.
 13. The method of claim 9, further comprising heating thepreform to an initial temperature prior to engaging the preform with thespool.
 14. The method of claim 9, wherein the desired spool speed isbased, at least in part, on a desired diameter of the optical fiber. 15.The method of claim 9, wherein turning the spool comprises applying atorque to the spool by a computer-controlled motor.
 16. The method ofclaim 9, wherein providing the preform in a preform drawing apparatus inthe low gravity environment comprises providing the preform in aplatform or vehicle orbiting the Earth.
 17. An optical fiber drawn in alow gravity environment in accordance with the method of any of claims9-16.
 18. The optical fiber of claim 17, wherein the optical fibercomprises fluoride.
 19. The optical fiber of claim 18, wherein theoptical fiber comprises ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN).
 20. The opticalfiber of claim 17, wherein the optical fiber comprises an insertion lossin a range from 13 dB per 1000 km to 120 dB per 1000 km.